title: Water quality parameters controlling the photodegradation of two herbicides in surface waters of the Columbia Basin, Washington.
abstract: The water quality parameters nitrate-nitrogen, dissolved organic carbon, and suspended solids were correlated with photodegradation rates of the herbicides atrazine and 2,4-D in samples collected from four sites in the Columbia River Basin, Washington, USA. Surface water samples were collected in May, July, and October 2010 and analyzed for the water quality parameters. Photolysis rates for the two herbicides in the surface water samples were then evaluated under a xenon arc lamp. Photolysis rates of atrazine and 2,4-D were similar with rate constants averaging 0.025 h(-1) for atrazine and 0.039 h(-1) for 2,4-D. Based on multiple regression analysis, nitrate-nitrogen was the primary predictor of photolysis for both atrazine and 2,4-D, with dissolved organic carbon also a predictor for some sites. However, at sites where suspended solids concentrations were elevated, photolysis rates of the two herbicides were controlled by the suspended solids concentration. The results of this research provide a basis for evaluating and predicting herbicide photolysis rates in shallow surface waters.
authors.affiliation: Department of Civil & Environmental Engineering, Washington State University, Pullman, WA 99163-2910, United States. Electronic address: ofurman@umn.edu.
authors.forename: Olha S
authors.initials: OS
authors.lastname: Furman
authors.forename: Miao
authors.initials: M
authors.lastname: Yu
authors.forename: Amy L
authors.initials: AL
authors.lastname: Teel
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Watts
mesh_terms: D004784:Environmental Monitoring; D006540:Herbicides / Q000032:analysis*; D010782:Photolysis; D045483:Rivers / Q000737:chemistry*; D014861:Washington; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical
keywords: 2,4-Dichlorophenoxyacetic acid (2,4-D); Atrazine; Columbia River Basin; Photolysis